The dastardly contraption was one of thousands of balloon bombs launched toward North America in the 1940s as part of a secret plot by Japanese saboteurs. To date, only a few hundred of the devices have been found — and most are still unaccounted for.

The plan was diabolic. At some point during World War II, scientists in Japan figured out a way to harness a brisk air stream that sweeps eastward across the Pacific Ocean — to dispatch silent and deadly devices to the American mainland.

The project — named Fugo — "called for sending bomb-carrying balloons from Japan to set fire to the vast forests of America, in particular those of the Pacific Northwest. It was hoped that the fires would create havoc, dampen American morale and disrupt the U.S. war effort," James M. Powles describes in a 2003 issue of the journal World War II. The balloons, or "envelopes", designed by the Japanese army were made of lightweight paper fashioned from the bark of trees. Attached were bombs composed of sensors, powder-packed tubes, triggering devices and other simple and complex mechanisms.

'Jellyfish In The Sky'

"The envelopes are really amazing, made of hundreds of pieces of traditional hand-made paper glued together with glue made from a tuber," says Marilee Schmit Nason of the Anderson-Abruzzo Albuquerque International Balloon Museum in New Mexico. "The control frame really is a piece of art."

As described by J. David Rodgers of the Missouri University of Science and Technology, the balloon bombs "were 33 feet in diameter and could lift approximately 1,000 pounds, but the deadly portion of their cargo was a 33-lb anti-personnel fragmentation bomb, attached to a 64–foot-long fuse that was intended to burn for 82 minutes before detonating."

Once aloft, some of the ingeniously designed incendiary devices — weighted by expendable sandbags — floated from Japan to the U.S. mainland and into Canada. The trip took several days.

"Distribution of the balloon bombs was quite large," says Nason. They appeared from northern Mexico to Alaska, and from Hawaii to Michigan. "When launched — in groups — they are said to have looked like jellyfish floating in the sky

Mysterious Munitions

Sightings of the airborne bombs began cropping up throughout the western U.S. in late 1944. In December, folks at a coal mine close to Thermopolis, Wyo., saw "a parachute in the air, with lighted flares and after hearing a whistling noise, heard an explosion and saw smoke in a draw near the mine about 6:15 pm," Powles writes.

Another bomb was espied a few days later near Kalispell, Mont. According to Powles, "An investigation by local sheriffs determined that the object was not a parachute, but a large paper balloon with ropes attached along with a gas relief valve, a long fuse connected to a small incendiary bomb, and a thick rubber cord. The balloon and parts were taken to Butte, [Mont.] where personnel from the FBI, Army and Navy carefully examined everything. The officials determined that the balloon was of Japanese origin, but how it had gotten to Montana and where it came from was a mystery."

Eventually American scientists helped solve the puzzle. All in all, the Japanese military probably launched 6,000 or more of the wicked weapons. Several hundred were spotted in the air or found on the ground in the U.S. To keep the Japanese from tracking the success of their treachery, the U.S. government asked American news organizations to refrain from reporting on the balloon bombs. So presumably, we may never know the extent of the damage.

Danger: UXB

We do know of one tragic upshot: In the spring of 1945, Powles writes, a pregnant woman and five children were killed by "a 15-kilogram high-explosive anti-personnel bomb from a crashed Japanese balloon" on Gearhart Mountain near Bly, Ore. Reportedly, these were the only documented casualties of the plot.

Another balloon bomb struck a power line in Washington state, cutting off electricity to the Hanford Engineer Works, where the U.S. was conducting its own secret project, manufacturing plutonium for use in nuclear bombs.

Just after the war, reports came in from far and wide of balloon bomb incidents. The Beatrice Daily Sun reported that the pilotless weapons had landed in seven different Nebraska towns, including Omaha. The Winnipeg Tribune noted that one balloon bomb was found 10 miles from Detroit and another one near Grand Rapids.

Over the years, the explosive devices have popped up here and there. In November 1953, a balloon bomb was detonated by an Army crew in Edmonton, Alberta, according to the Brooklyn Daily Eagle. In January 1955, the Albuquerque Journal reported that the Air Force had discovered one in Alaska.

In 1984, the Santa Cruz Sentinel noted that Bert Webber, an author and researcher, had located 45 balloon bombs in Oregon, 37 in Alaska, 28 in Washington and 25 in California. One bomb fell in Medford, Ore., Webber said. "It just made a big hole in the ground."

The Sentinel reported that a bomb had been discovered in southwest Oregon in 1978.

The bomb recently recovered in British Columbia — in October 2014 — "has been in the dirt for 70 years," Henry Proce of the Royal Canadian Mounted Police toldThe Canadian Press. "It would have been far too dangerous to move it."

So how was the situation handled? "They put some C-4 on either side of this thing," Proce said, "and they blew it to smithereens."